For recording media to record music contents, motion picture contents, still image contents, and other various kinds of digital data (hereinafter called the “content”), there exist a wide variety of media including semiconductor recording media, magnetic disks, optical disks, magneto-optical disks, and others.
In particular, semiconductor recording media have features of small size and light weight, and in recent years, increased capacity, increased speed, and price reduction are rapidly taking place, and are able to be used in various devices including digital cameras, cellular phones, portable music players, TV sets, and DVD recorders. Examples of typical semiconductor recording media include SD Memory Card (registered trademark), Memory Stick (registered trademark), Compact Flash (registered trademark), and so on.
The semiconductor medium of SD Memory Card, and so on which have copyright protection functions, can prevent unauthorized copying, and can safely record proprietary content.
One example of content storage method which has been achieved in semiconductor media with copyright protection function is described as follows.
The semiconductor recording medium includes a protection area which a host device is allowed to be accessed only by authenticating the mutual validity between a semiconductor recording medium and host device (reproducing device or recording device, etc.) and a normal area to which the host device can gain free access. And in the normal area, encrypted content is recorded and a key for encrypting the content (hereinafter called the “content key”) is stored in the protection area. The content recorded in this way can prohibit playback by an unauthorized device which fails mutual authentication. This is because the unauthorized device can not read the content key and not decode the encrypted content. Furthermore, even if the encrypted content only stored in the normal area is copied into other recording medium, the unauthorized device is unable to copy the content key, and thus no content key exists in the copy destination recording medium. Consequently, playback of the unauthorized copied encrypted content can be prohibited.
Conventionally, for content to be stored in a semiconductor recording medium with copyright protection function by the above-mentioned storing method, music content, etc. ripped from music CDs which users purchased were dominant.
However, in recent years, various applications have been developed for various kinds of contents using copyright protection functions of the semiconductor recording medium.
For example, it has become possible to download content with copyrights of music and books from content providers using a PC connected to Internet by paying the required price, store the downloaded content in the semiconductor recording medium, and enjoy the music content or read the book content stored in the semiconductor medium by a small-size semiconductor player.
In addition, it is possible to purchase content not only in PC connected to Internet but also in electronic terminals (KIOSK terminals) located in specific places such as convenience stores, specified shops, and stations. Because these applications provide users with high convenience and expand various selling networks for content providers, too, it is assumed that still more diversified kinds of content and use environment come in wide use in the future.
Specifications for storing various kinds of contents with copyright in the semiconductor recording medium as described above are generally defined in accordance with characteristics of semiconductor recording medium and various kinds of contents. A recording device records content according to the specifications. This allows content to be played back by a reproducing device which conforms to the specifications.
More specifically, to take a music application program as an example, the content which corresponds to music is encrypted by a content key, and the content key and encrypted content are stored in a semiconductor recording medium.
Patent document 1 discloses a semiconductor recording medium that stores multiple content keys in a protection area by the arrangement of the specified order, and stores the encrypted contents and management information for them in a normal area. This semiconductor recording medium can easily sort music playback order or delete a part of music contents while preventing illegal copy of music contents, resulting in extremely high convenience.    Patent document 1: JP-A-2001-249695